The invention relates to a quick closure box comprising a molded material base and a lid fixed thereon by means of screws each passing through an opening in this lid and having a threaded end with a small diameter and small pitch which is engaged in a tapped hole belonging to a coaxial cylindrical extension having externally a large pitch thread of a diameter greater than the preceding one, this second thread being in its turn engaged in a second fixed tapped hole which is disposed in the base in the vicinity of a wall thereof.
Such boxes, which are in particular very widely used in electrical installations, receive in this case electric apparatus to be protected from the outside such, for example, as contact makers, contact breakers, thermal relays or any other accessory necessary for their connection which are fixed in the base, as well as possibly switches, change-over switches, indicator lights which are frequently fixed to the lid.
When the electric installations occupy a considerable volume because of the large number of electric apparatus which they use, the time required for positioning, connecting and closing the boxes occupies a considerable fraction of the tasks of the installing staff and, consequently, any technical means likely to shorten them is considered as a not inconsiderable intrinsic value of the equipment.
Arrangements have then been sought for appreciably reducing the time required for opening and closing the boxes using the means mentioned above. The arrangements already made further comply with two additional objectives which are, on the one hand, that of applying the lid with sufficient force to suitably compress the seal placed between the base and the lid and, on the other hand, that of using plastic material screw tappings which do not wear out during engagement with the metal threads which cooperate therewith.
A constant preoccupation in all industries is that of lowering the technical manufacturing costs which frequently involves simplifying the production means.
When tappings are formed on plastic material molded parts, the molds are generally equipped with threaded pins which can only be extracted, when their diameter is reduced, by rotating them.
The time devoted to such extraction represents a determining fraction of the total time required for opening the mold and any handling economy during this operation will constitute an appreciable gain in productivity. Furthermore, such rotary pins are substantially more costly and more subject to malfunctions than the slides which function with a simple rectilinear movement, for example transversely to the main removal direction.
Consequently, the invention proposes improving a quick closure box, whose general construction is that mentioned above in order to keep the advantages which are attached thereto, which improvements make possible not only improvement in productivity but also a great reduction of the time required for its opening and closure.